[Dave Flowerday]

Not sure how closely it fits what you're looking for, but all recent Motorola iDEN phones (Nextel & BoostMobile) have GPS units built in. You can turn on NMEA 0183 output from these and access it over either serial or USB depending on which data cable you get. You might be able to find someone with an older i730 or something that they'd give you, or else you can find the Boost i415 for about $30 at places like Target & Wal-Mart. $10 will probably get you the data cable from eBay.

{edit} You don't need to have it activated to use the GPS, and the Boost i415 is a pre-paid so it can be bought w/o contract. {/edit}